#include <iostream>
#include <vector>
using namespace std;

int main()
{
    int n, m;
    cin >> n >> m;
    long long pp1, pp2, np1, np2;
    pp1 = n / 5;
    pp2 = m / 5;
    np1 = n % 5;
    np2 = m % 5;
    long long colvo;
    colvo = 5 * pp1 * pp2 + np2 * pp1 + np1 * pp2;
    if ((np1 + np2) >= 5)
        colvo += (np1 + np2) % 5 + 1;
    cout << colvo;
}